Cleaning applications typically involve the removal of foreign matter off surfaces. In laundry applications, this involves the removal of both hydrophobic and hydrophilic soils (food stains, blood, grass, dirt, grease, oils, etc.) off various fabrics including cotton, polyester, silk, rayon, wool and various blends of these materials.
For laundry applications, the consumer has two choices for removal of soils: conventional water based cleaning and dry cleaning (i.e., non-aqueous based cleaning). Compositions suitable for use in conventional water based fabric cleaning systems have been optimized over the years. Specifically, laundry detergents that include surfactants, enzymes, builders, bleaches, chelants, polymers and other additives have been shown to remove both hydrophilic and hydrophobic soils efficiently in a water based fabric cleaning system. More specifically, while cotton, polyester and various blends can be efficiently cleaned using conventional water based systems, other more delicate fabrics, such as silk, wool, and rayon, are prone to fabric damages or shrinkages caused by the water based cleaning process and generally rely on the dry cleaning process.
The dry cleaning process refers to a process where low or no water is used in the cleaning system; it uses various non-aqueous organic solvents, such as halocarbons, hydrocarbons, densified carbon dioxide, glycol ethers and silicones.
Conventional detergent compositions and additives are designed for water based cleaning. It has been found that those conventional detergent compositions and additives are not effective fabric cleaning agents in dry cleaning solvents due to low compatibility with these solvents.
Some additives, such as detersive surfactants, have been developed for dry cleaning applications. An important design feature of these additives is their enhanced compatibility with the dry cleaning solvents. Not limited in theory, it is believed that these detersive surfactants can boost detergency by solubilizing the target soils; by suspending water in the dry cleaning solvents or system, if low levels of water are utilized; and by forming reverse micelles that help trapping soils for removal from the fabric treating system. Surfactant detergency has been discussed in “Detergency of Specialty Surfactants”, by F. E. Friedli, Marcel Dekker, Inc., NY (1988). Use of surfactants in a dry cleaning application has been disclosed in U.S. Pat. No. 5,944,996; U.S. Pat. No. 6,548,466; U.S. Pat. No. 6,461,387; U.S. Pat. No. 6,148,644; and U.S. Pat. No. 6,114,295.
Accordingly, there is a continuing need to develop fabric treating agents to enhance soil removal and other fabric treating benefits in non-aqueous cleaning applications.
It is well known that after being used in a laundering treatment, the dry cleaning solvents typically contain fabric treating agents, such as surfactants, soil release polymers, bleaches, enzymes, and other adjunct ingredients. Since the dry cleaning solvents are more expensive than water, there is a need to recycle/reuse the dry cleaning solvents in more than one treatment. Conventional purification process uses distillation to remove the fabric treating agents from the dry cleaning solvents. However, equipment and conditions to run a distillation method are extremely burdensome, energy consuming, and not practical for use in a consumer's home. Accordingly, there is a need to remove fabric treating agents from dry cleaning solvents without distillation. Representative systems using the distillation method are disclosed in EP 543,665 and U.S. Pat. Nos. 5,942,007; 6,056,789; 6,059,845; and 6,086,635.
A typical non-distillative purification method employs filter containing clay and/or activated carbons. Representative filters containing carbon and clay adsorbent materials are disclosed in U.S. Pat. Nos. 4,277,336 and 3,658,459, and some are commercially available KleenRite® filter. However, such filter has a rather limited lifetime before it has to be replaced and are less efficient in removing fabric treating agents.
Therefore, there is a need for a method that effectively removes fabric treating agents, especially surfactants from a dry cleaning solvent so that the purified solvent can be recycled/reused.
There is also a need to have a method capable of purifying a dry cleaning solvent in a safe, economical and energy efficient manner. Therefore, there is a need for a non-distillation method that removes fabric treating agents from the dry cleaning solvent at low temperature and ambient pressure.
Based on the foregoing, it is desirable to have a method that chemically modifies or converts the contaminants into less soluble compounds/molecules, which can be easily removed from the dry cleaning solvent. It is also desirable to have a method that changes the characteristics of the mixture thereby rendering the contaminants less soluble in the mixture such that the contaminants can be easily separated from the mixture. It is further desirable to have a purification process comprising both methods to further enhance the separation of the contaminants from the lipophilic solvent.